Numerous methods, ophthalmic devices, and medical equipment are available to surgeons to alter the refractive power of the eye. One of the most common methods involves altering the anterior corneal curvature, which comprises approximately 2/3 of the eye's optical power. Such surgical methods presently in use include radial keratotomy (RK), excimer laser photorefractive keratectomy (PRK) laser and in-situ Keratomileusis (LASIK). None of these techniques correct a full range of refractive errors, nor have they been found to correct irregular astigmatism, a problem encountered in many patients following previous refractive surgical procedures, corneal trauma, keratoconus, and other conditions that produce an abnormal corneal shape. LASIK and PRK require irreversible removal of corneal tissue.